Packages are used to enclose the content during storage and transport, to protect the content so as to keep their qualities from filling until emptying of the package, and often also to market the content. It has proved especially difficult to design packages for maintaining the original properties of contents, such as foodstuff, medicine or cigarettes. The quality of the content may be reduced either by the content itself changing as time goes on or by quality-reducing substances being supplied from or through the package. The content can be treated, e.g. pasteurized, as with milk; or dried, as with flour. Usually, the packages are designed with several layers which often are made of different materials. Thus, each layer and each material has a specific quality and purpose in the package, such as preventing the transfer of oxygen, water or water vapour to the foodstuff.
Packaging materials are much used as components in packages to keep solid foodstuff or liquid foodstuff, such as milk, juice, wine and water. Packages for beverages usually are made of rigid paperboard comprising several different layers of lignocellulose-containing fibres, combined with one or more layers of plastic in direct contact with the beverage. Despite the use of such specially designed combinations of materials, the beverages usually acquire an undesirable taste after some time. It has been found that the substances causing undesirable taste in the beverage often are oxidation products formed during production and storage of the paperboard. Since the packaging material is kept on rolls or in bales of sheets before the finished packages have been shaped and filled with food, the oxidation products may be transferred to the plastic-coated inside of the package. Thus, it is desirable to reduce not only the formation of substances causing undesirable taste in the production of packaging materials, but also the transfer of substances causing undesirable taste present in the packaging material from the start or formed during its production.
SE patent specification 8006410-8 discloses the pretreatment of a box blank subjected to neutral or alkaline sizing in order to reduce the formation of such degradation products as aldehydes and ketones formed by autoxidation. Thus, chips and/or the mechanical pulp produced from the chips are treated with alkali and subsequently washed or dewatered in one or several steps. Naturally, more process steps make the process more complicated as well as more expensive. Also, the process does not solve the problems associated with other substances causing undesirable taste than those present in the chips. Thus, an addition of paper chemicals, such as retention agents, dewatering agents and sizing agents, may increase the problem of undesirable taste of the food.